/*
 * NumberAttributeRenderer.java
 *
 * Copyright 2010 Jack Leow
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package my.edu.clhs.stringtemplate.renderer;

import java.text.DecimalFormat;
import java.text.FieldPosition;
import java.text.NumberFormat;
import java.util.HashMap;
import java.util.Map;

import org.antlr.stringtemplate.AttributeRenderer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * StringTemplate {@link AttributeRenderer} for Java SE {@link Number}s.
 *
 * @author Jack Leow
 * @version 1.0
 * @since 1.0 (Dec 26, 2010, 10:02:03 PM)
 */
public class NumberAttributeRenderer implements AttributeRenderer {
    private static final Logger log =
        LoggerFactory.getLogger(NumberAttributeRenderer.class);
    
    /**
     * Cache for date formatters. This is {@link ThreadLocal} as
     * {@link DecimalFormat}s are not thread-safe per its API documentation.
     */
    private static final ThreadLocal FORMATTER_CACHE = new ThreadLocal() {
        protected Object initialValue() {
            return new HashMap();
        }
    };
    
    private DecimalFormat getFormatter(String format) {
        Map formatterCache = (Map)FORMATTER_CACHE.get();
        DecimalFormat formatter = (DecimalFormat)formatterCache.get(format);
        if (formatter == null) {
            formatter = new DecimalFormat(format);
            formatterCache.put(format, formatter);
        }
        
        return formatter;
    }
    
    public String toString(Object o) {
        log.debug("entering toString(Object)");
        log.debug("exiting toString(Object)");
        return o != null ? o.toString() : null;
    }
    
    public String toString(Object o, String format) {
        log.debug("entering toString(Object,String)");
        String str;
        
        if (o != null) {
            str = getFormatter(format).format(o, new StringBuffer(),
                new FieldPosition(NumberFormat.INTEGER_FIELD)).toString();
        } else {
            str = null;
        }
        
        log.debug("exiting toString(Object,String)");
        return str;
    }
}